(Supported by the NIH NCRR/P41 RR 01219 grant) Sterecon is a software system developed at the BMIRR for interactive tracing and measurement of structures in microscopy images of every type, with the special feature of tracing in 3-D using stereoscopic viewing. A recent full description of Sterecon was published (Marko and Leith (1996) J. Structural Biol. 11693-98), in which the system is offered for distribution. Sterecon is also described on its homepage at www.wadsworth.org/spider_doc/sterecon/sterecon.html At the BMIRR, Sterecon is used for analysis of stereopairs from HVEM or IVEM thick sections, and also for analysis of confocal z-series volumes. It is used for segmentation of nearly every electron tomographic volume made at the BMIRR, as the first step in making striking illustrations and animations using Sterecon's interfaces to SGI Explorer and SceneViewer for surface rendering. A current version of Sterecon, written using Open GL, has modern user interface for display of reconstructions. The use of Open GL means that it will be possible to port this new version to the PC. Sterecon development is continuous because of adaptations required for specific research projects, and because updates in computer hardware and operating systems often require changes to maintain compatibility across all current SGI systems. For a project involving high-resolution cryo-SEM by Dr. Stan Erlandsen of U. Minnesota (see DIS sub project "Sterecon dissemination"), a module to automatically align stereopair images, and a module to easily determine the surface area of defined patches of the cell surface were developed. These modules improved the speed and convenience of use. A retractable polarization/beamsplitter mirror system was designed and built. This allows the use of two-monitor stereoscopic viewing, which provides higher resolution and greater viewing comfort than the single-monitor stereo-viewing system commonly in use, and requires only inexpensive passive polarizing glasses. This system was used on the first version of Strerecon a decade ago. Software modules for two-monitor viewing are now being debugged. Sterecon interface modules for export of traced contours to other visualization software such as MOVIE.BYU for contour tiling, Iris Explorer for surface rendering, and SceneViewer model building, as well to SPIDER for general image processing, were improved. In addition to more complete transfer of contour-description parameters, models made with all the visualization programs mentioned now have the same scale in 3-D. The Edge company, manufacturers of light microscopes with 3-D viewing capability, expressed an interest in marketing Sterecon as an adjunct to their product. After considerable discussion and deliberation, the company decided just to recommend Sterecon as a software system of interest to their customers. A group at the AutoQuant company and Rensselaer Polytechnic Institute used Sterecon to verify 3-D length, volume, and surface area measurements obtained with their software package for confocal light microscopy. A paper was written: O'Connor, N,J,, Turner, J.N., Szarowski, D.H., Marko, M., Holmes, T.J. (1998) Blind deconvolution of three-dimensional laser scanning confocal imagery: Recent advances and testing. J. Microscopy (submitted).